Piezoelectric actuator and liquid-droplet jetting head

Abstract

A piezoelectric actuator includes a first ceramic sheet having individual inner-electrodes formed thereon, a second ceramic sheet having a common inner-electrode formed thereon, a third ceramic sheet having individual surface-electrodes formed thereon, and a fourth ceramic sheet having a plurality of connection electrodes connecting the individual surface-electrodes and the individual inner-electrodes respectively. The connection electrodes have first portions, second portions and third portions respectively, the first portions facing the individual surface-electrodes and arranged at a pitch in a row in a row-direction, the second portions facing the individual inner-electrodes and being arranged in the row-direction to be shifted with respect to the first portions by half the pitch respectively; and the third portions connecting the first portions and the second portions respectively. Accordingly, the electrodes can be made compact or arranged highly densely without lowering the conductance between the electrodes.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]The present application claims priority from Japanese Patent Application No. 2006-155484 filed on Jun. 3, 2006, the disclosure of which is incorporated herein by reference in its entirety.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a piezoelectric actuator and a liquid-droplet jetting head.[0004]2. Description of the Related Art[0005]As a conventional ink-jet head, there is known an ink-jet head having a cavity unit which is constructed by stacking a plurality of sheets and which has a plurality of pressure chambers formed and aligned in a plurality of rows therein, and a piezoelectric actuator which has active portions (energy-generating mechanism) corresponding to the pressure chambers respectively and which is joined to the cavity unit. For example, as shown in FIG. 4 of U.S. Patent Application Publication No. US2005 / 162484A1 and FIG. 4 of U.S. Patent Application Publication No. US200...

AI Technical Summary

Benefits of technology

The present invention provides a piezoelectric actuator with a plurality of ceramic sheets stacked together and containing individual inner-electrodes and pressure chambers. A common inner-electrode and a common surface-electrode are formed on the top surface of the ceramic sheets. The actuator also includes individual surface-electrodes and individual inner-electrodes that are connected to the individual surface-electrodes and individual inner-electrodes, respectively, through connection electrodes. The connection electrodes have first, second, and third portions that are arranged in a row-direction to be shifted with respect to each other. This arrangement allows for absorbing any shift in the position of the individual inner-electrodes caused by the close proximity of the portions connected to the individual surface-electrodes and the individual inner-electrodes. The actuator also includes terminals for connecting signal lines to the individual surface-electrodes and the common surface-electrode. This makes it easy to arrange the electrical wiring on the outermost layer of the actuator.

Problems solved by technology

In such a piezoelectric actuator, when a flexible flat cable is joined to the surface electrodes for the individual electrodes and the pressing force generated upon the joining acts on portions above the cavity-shaped pressure chambers, there is a fear that the ceramic sheet or sheets is / are broken.

In this case, it is difficult to print and form short electrodes each having a sharply bent portion with high precision, and there is a fear that any conduction failure occurs in the bent portions.

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